TRANSPORT

Transmission and Interconnections

The National Transmission Network (RNT in its Portuguese acronym) will continue to grow in the post-2017 period and will interconnect in 2025 all of the country’s Provincial capitals. A significant part of the Very High-Voltage network is already foreseen in the Action Plan, therefore the growth rate of the National Transport Network during the 2018-2025 period will be smaller and more focused on the 60 kV investments needed to support rural electrification.

The total length of transmission lines will go from 2.850 km in 2013 (60, 220 and 400 kV lines) to 16.350 km in 2025. The number of substations belonging to the National Transport Network will also increase from 36 in 2013 to 152 in 2025, with a marked increase of 60 kV substations (charts in figure below).
The following map shows the planned National Transport Network evolution overlapped with the Angola 2025 map of territorial development. It can be observed that the network growth will follow the country’s development corridors, showing a strong alignment between the power sector evolution until 2025 and the Angola 2025 Strategy.

EVOLUTION OF THE LENGHT AND SUBSTATION NUMBER OF RNT

NATIONAL NETWORK MAP IN 2025 AND DEVELOPMENT CORRIDORS

The following National Network investments in the post-2017 period are noteworthy:

New 220 kV corridor with a double transmission line between north and east. The selection of the 220 kV option is due to the fact that a n-1 redundancy and security level is required;

A 400 kV corridor from Queve towards Namibia in the south going through Benguela and Lubango - thus completing the 400 kV north-south backbone. This new corridor will be closer to the coastline, providing the necessary flexibility to, in the future, flow power from generation based on a new gas supply site;

A new 220 kV axis to reinforce the supply to Menongue;

The ring network closure of the 220 kV antennas in the Northern system, connecting M’Banza Congo and Maquela do Zombo.

SINGLE LINE DIAGRAM OF THE ELECTRIC TRANSMISSION SYSTEM ANGOLA ENERGY 2025 - ANAREDE Simulation

Interconnections

The interconnection of Angola to the SADC regional network is of high importance given the strong focus in hydroelectric power. In highly favorable hydrologic years Angola will have an excess of energy that it will either have to export or discharge. In “dry” years the possibility to import energy
during off-peak hours from South Africa’s coal-fired power plants will facilitate system operation during off-peak hours at lower costs.

In terms of interconnections with neighboring countries, the following lines are to be agreed and implemented until 2025:

To the north, 3 connections to the DRC: between Soyo and Inga at 400 kV; between Cabinda and Inga at 220 kV and between Luachimo and Kananga at 220 kV also;

To the south, connections to Namibia: via Baynes at 400 kV, via Ondjiva, which will be connected to the network at 60 kV;

In addition border connections to Namibia to supply Calueque, Cuangar, Calai and Dirico.

The connection to DRC will reinforce Cabinda’s energy security and, depending on the Inga’s completion calendar, export energy to the city of Kinshasa. To the east the connection to Kananga will help reinforce the system’s stability.

particular during the months of less hydropower production – due to the importance of Ruacaná hydro scheme. Namibia is also highly interconnected to the region, representing therefore an important link to South Africa, Zimbabwe and Zambia. Baynes hydroelectric power station, to be developed
in cooperation, constitutes the natural interconnection point at 400 kV.

It is also proposed a new optional axis to be developed in HVDC to the “Copper Belt” area in Zambia. However, this axis should only be developed if supported by private initiative. In this scenario, Angola could provide to the promoters the possibility of building the Túmulo do Caçador hydro scheme and a combined cycle power plant in Lobito.

MAP OF INTERCONNECTIONS AND REGIONAL TRANSMISSION LINES

National Transmission Network utilization and interconnections

The map shows a simplified vision of the utilization of the National Network during an average hydrologic year, namely the main direction of the energy flows between the main nodes of the network, the volume of energy transmitted and the utilization rate of the different corridors. For each node
the generation’s marginal cost along the year is calculated – marginal cost tends to increase with the number of restrictions occurring in transmission.
The 400 kV corridor takes an increasing structural importance in energy transmission in 2025, given that most of the energy flows at this tension level:
The biggest energy flow occurs from Soyo and the Kwanza based hydro power plants in the direction of Luanda, and no restrictions are observed;

The 400 kV connection between the north and the center and between the center and the south presents a higher occupancy rate with an increase in the generation’s marginal price as we move towards the south. As for the 220 kV corridors we can point out the corridor between the Jambas hydro schemes and the southern system (Lubango and Menongue) that will be used to its full capacity, as well the corridor between the north and the east with also a high utilization rate.

The price differences between the various nodes are not significant with the exception of the Southern, Eastern and Cabinda’s Systems, where the prices are higher. This similarity in prices and the reduced corridor restrictions are indications that the system is close in behavior to a single interconnected network. Interconnections will allow to export energy in an average year and, in what concerns the south, also import energy during dry years and off-peak hours.

ENERGY FLOW SIMULATIONS AND MARGINAL COSTS FOR AN AVERAGE YEAR (GTMAX)

Luanda

In the particular case of Luanda, the investments planned until 2017 will allow to support the load increase of the city until the expected 3,3 GW load, with the exception of the Viana substation. In 2025, according to the simulations performed, the electricity that flows at 400 kV in the direction of Luanda
will tend to flow towards Viana, exceeding by far the 400/220 kV transformation capacity available should there be no new investments.

In order to avoid this problem, a series of measures are to be implemented until 2025 so as to minimize and manage the pressure on the Viana substation in the future:

Creation of a 400 kV switchyard in the Cacuaco substation in order to section the 400 kV Kapary-Catete transmission line;